Photographic silver halide emulsion containing as a sensitizer bio-quarternary salts of bis-aminoalkyl-disulfides

ABSTRACT

The sensitivity of photographic silver halide emulsions can be increased and the fogging of those emulsions can be decreased by using bis-quaternary salts of bis-aminoalkyl-disulfides of the following formula: WHEREIN R is alkyl, two R radicals at the same N may form together with the N a heterocyclic ring; R&#39;&#39; is alkyl or aralkyl; N is 1-6, and X is any anion; THE COMPOUNDS CAN BE USED AS RIPENING AGENTS OR AS ADDITIVES TO THE CASTING SOLUTION OR TO THE DEVELOPER.

United States Patent [151 3,640,715 Hiickstfidt et al. 1 Feb. 8, 1972 54] PHOTOGRAPHIC SILVER HALIDE 3,057,725 l0/l962 Herz et a]. ..96/l09 EMULSION CONTAINING AS A 3,419,392 12/1968 Thompson ..%/l07 SENSITIZER BlO-QUARTERNARY SALTS 0F BIS-AMINOALKYL- DHSULFIDES Inventors: Harald Hiickstidt, Cologne; Wilhelm Saleck, Schildgen/Berg. Gladbach; August Randolph, Leverkusen; Franz Moll, Cologne; Erwin Ranz, Leverkusen, all of (iermany Assignee: Agfa-Gevaert Aktiengesellschaft, Leverkusen, Germany Filed: Dec. 17, 1969 Appl No.: 886,039

Foreign Application Priority Data Dec. 23, 1968 Germany ..P 18 16 5725 US. Cl ..96/55, 96/66, 96/665, 96/107, 96/109 Int. Cl ..G03c 7/00, G03c 5/30, G030 1/28 Field of Search ..96/l07, 109, 66, 55, 66.5

References Cited UNITED STATES PATENTS Mueller ..96/ 109 Primary ExaminerNorman G. Torchin Assistant Examiner-Richard E. Fichter AttorneyConnolly 8L Hutz ABSTRACT The sensitivity of photographic silver halide emulsions can be increased and the fogging of those emulsions can be decreased by using bis-quaternary salts of bis-aminoalkyl-disulfides of 9 Claims, No Drawings PIIOTOGRAPIIIC SILVER IIALIDE EMULSION CONTAINING AS A SENSITIZER BIO-QUARTERNARY SALTS OF BIS-AMINOALKYL-DISULFIDES The present invention relates to a process for increasing the sensitivity of photographic silver halide emulsions together with reduced fogging by the addition of bis-quatemary salts which contain a disulfide linkage.

The sensitivity of a photographic emulsion can be affected in two ways. First, the sensitivity can be increased in the course of preparation of the emulsion at the stage of so-called chemical ripening, by increasing the ripening time or by adding suitable substances such as thiosulfate or other compounds which usually contain sulfur. The other method of increasing the sensitivity of a'photographic emulsion consists of adding so-called development accelerators or chemical sensitizers. These are usually added to the completely ripened emulsion.

Development accelerators which have been described for this purpose are, for example, compounds which have an onium structure (such as quaternary ammonium and pliosphonium salts and ternary sulfonium salts) and also polyalkylene oxides and derivatives thereof are very frequently employed.

Nearly all these ingredients, however, have the unfavorable side effect of increasing the fogging of the emulsion. In order to counteract this increase in fogging, which may occur not only in the heating cupboard, but also in the fresh sample, it is in most cases necessary to increase the quantity of stabilizer, but most stabilizers have a characteristic such that they reduce the sensitivity when used in large quantities. The effect of the development accelerator can thereby be impaired.

There was. therefore, an urgent need to find development accelerators or ripening compounds which would not bring about any additional increase in fogging, and there is also an urgent need to find stabilizers which will not impair the sensitivity of the photographic emulsion. It is desirable to find substances which would both increase the sensitivity of the photographic emulsion and also stabilize the fogging.

This is the object of the present invention.

It has now been found that silver halide emulsions having increased sensitivity and reduced fogging are obtained by adding to the said emulsions, bisquaternary salts of diaminoalkyl disulfides of the following general formula:

wherein R an alkyl radical having up to six carbon atoms; two R radicals attached to the same N atom may be conjoined so as to form together with the N atom a saturated 5-, 6- or 7-membered heterocyclic ring, which may also contain further hetero atoms, such as for example piperidine, morpholine, thiomorpholine, piperazine, pyrrolidine, hexamethyleneimine, or an unsaturated heterocyclic ring such as pyridine; in the latter case R is not present; R on alkyl radical having up to six carbon atoms which may be substituted, for example, a hydroxyalkyl, cyanoalkyl, haloalkyl or carboxyalkyl, an aralkyl radical such as benzyl or phenylethyl; the phenyl radical may be substituted (e.g., by chlorine, Nl-l OH, alkyl or other substituents); n an integer of from 1 to 6; and X any organic or inorganic anion such as chloride, bromide perchlorate, or toluenesulfonate; X is not present, when R contains a carboxylate group.

The following formulas are given as examples for the purpose of illustrating the above general formula, but are not intended to limit the scope of the invention:

Tim/Q 'GHZQ CaHs C211 XXI The preparation of the compounds to be used according to the invention is carried out in a known manner. Thus a dialkylaminoalkyl mercaptan prepared via an isothiouronium salt may be oxidized with suitable agents to form bis-(dialkylaminoalkyl)-disulfide which then may be quaternized in some suitable manner.

The disulfides required for quaternization can also be obtained conveniently from dialkylaminoalkyl chlorides via the alkali metal salts of w-thiosulfato-N,N-dialkylamino-alkanes.

The following specific methods serve to illustrate the method of preparation.

1. BlS-(DIMETHYLAMINOPROPYL)-DlSULFlDE 158 g. (1 mol) of 'y-chloropropyl-dimethylamino hydrobromide are dissolved in 500 ml. of methanol. A solution of 158 g. (1 mol) of anhydrous sodium thiosulfate in 500 ml. of water are added dropwise with stirring to the boiling methanolic solution. A solution of 112 g. of iodine (0.88 mol) in 500 to lOOO ml. of methanol is then added slowly in the course of 2 to 3 hours to the boiling reaction solution. The solution is then concentrated by evaporation. Approximately l.5 liters of a mixture of methanol and water are distilled off. The cooled concentrated solution is made alkaline with sodium hydroxide solution which contains 200 g. of solid NaOH in 500 ml. of water, and the reaction mixture is then extracted several times with chloroform. After the chloroform extract has been dried, the chloroform is evaporated off and the residue is distilled under vacuum.

B.p. at 2,] Torr: l29l 30C.

Yield: 60 g. -approximately 50 percent of the theory.

2. BlS-(TRlMETHYLAMMONlUM-PROPYL)-DlSULFlDE- BISTOSYLATE SUBSTANCE lX) 23.6 g. (0.1 mol) of the above-mentioned disulfide (Stage 1) are dissolved in 30 ml. of acetone, and 37:1 g. (0.2 mol) of methyl p-toluenesulfonate are carefully added with cooling. The mixture heats up and reacts quite vigorously.

It is left to stand at room temperature for 48 hours and then filtered with suction. The product is recrystallized from methanol-acetone.

Yield: 50=82 percent of the theory. M.p. 255-275 C.

3. BlS-(DIMETHYLBENZYLAMMONIUMPROPYL)- DISULFIDE DICHLORIDE SUBSTANCE XI 23.6 g. of the disulfide from Stage 1 are dissolved in 30 ml. of acetone, and 25.3 g. (0.2 mol) of benzyl chloride are added. The reaction mixture is left to stand for 48 hours at room temperature, filtered with suction and recrystallized from methanol-acetone.

Yield: 41 g.=84 percent of the theory. M.p. 2 l4-2 16 C.

The other compounds can be prepared in a similar manner. Some other methods for preparing bis-dialkylaminoalkyldisultides and their quaternary salts are given in Archiv der Pharmazie 293, (1960) pp. 55-67 and in .l.Org.Chem. 32, (1967) page 2,985 et seq.

The compounds according to the invention show their advantageous effect particularly clearly when they are used in place of thiosulfate or other sulfur compounds in chemical ripening. In addition to the increase in sensitivity described in the examples, the considerable reduction in the fogging in the samples is very striking. This reduction in fogging can be observed not only in fresh samples but also after the samples have been stored in the heating cupboard.

The effect of the substances according to the invention is, however, not limited to ripening. Similar, although not quite so marked effects can also be observed when using these compounds as casting additives. The specific advantage lies not so much in the increase in sensitivity, which can be regarded as only average, but in the combination of increase in sensitivity with reduction in fogging which enables other ingredients, which might possibly increase fogging, to be added to the emulsion without resulting in a net increase in fogging.

Emulsions prepared with the compounds according to the invention will, therefore, be particularly suitable for combining with other development accelerators. The reduction in fogging will also be very important for the preparation of color emulsions, since these are normally very susceptible to fogging.

The cause of the above-mentioned effect of quaternary salts which contain a disulfide linkage, in the ripening of the emulsions is still not clear, but it is known that in the presence of heavy metals, particularly silver, disulfides break down to form a large number of decomposition products, including mercaptans. This may be related to the cause of the particular effect of the compounds according to the invention.

US. Pat. No. 2,521,926 discloses the use of bis-(ydiethylaminopropyl)-disulfide as a ripening agent. Only one disulfide compound is described in the said patent, and it is stated there that its ripening action is different from that of the normal sulfur ripening agents. In the following examples, the hydrochloride of this compound and a few other diaminodisulfides have been given for comparison. From the experiments it will be seen that the effect according to the invention is confined to the quaternary salts, and that the effect is not achieved by bis-(dialkylaminoalkyl)-disulfides and their salts, which are not quaternized. Although these compounds have a certain albeit limited efiect in increasing the sensitivity, they lack the effect of reducing the fogging. The only exception to this is the compound H NC11 SSC1-1 CH N11 .2HCl (see our copending U.S. Pat. application Ser. No. 886,747; filed Dec. 19, 1964.

The substances according to the invention may be added to the photographic emulsion at any stage of its preparation, i.e., during or after chemical ripening. They may also be added to the casting solution directly before casting. The quantity added depends on the effect required, and can be determined by those skilled in the art at any time by the usual tests.

For chemical ripening it is generally sufficient to add 0.003-

to 20 g. of the inventive compounds per mol of silver halide. Concentrations of between 0.03 and 0.6 g. per mol of silver halide are preferred. If the substances according to the invention are added to the casting solution of the finished emulsion, the quantities required are generally slightly higher. They are then between 0.005 and 20 g., preferably between 0.003 and 6 g. per mol of silver halide.

The substances according to the invention may be used in any silver halide emulsions. Suitable silver halides are silver chloride, silver bromide or mixtures thereof, optionally with a small silver iodide content of up to 10 mols percent. The silver halides may be dispersed in the usual hydrophilic compounds such as carboxymethylcellulose, polyvinyl alcohol, polyvinyl pyrrolidone, alginic acid and its salts, esters or amides and preferably gelatin.

The emulsions may also contain other chemical sensitizers, e.g., quaternary ammonium and phosphonium salts and ternary sulfonium salts, reducing agents such as stannous salts, polyamines such as diethylene triamine, or sulfur compounds as described in U.S. Pat. No. 1,574,944. The given emulsions may also contain salts of noble metals such as ruthenium, rhodium, palladium, iridium, platinum, or gold for chemical sensitization, as described in the article by R. Koslowsky, Z.Wiss.Phot. 46, 65-72(1951).

The emulsions may also be optically sensitized, e.g., with the usual polymethine dyes such as merocyanines, basic or acid carbocyanines, rhodacyanines, hemicyanines, styryl dyes, or oxonoles. Sensitizers of this type have been described by F.M. Hamer in the book The Cyanine Dyes and related Compounds (1964).

The emulsions may contain the usual stabilizers, such as homopolar or salt type compounds of mercury with aromatic or heterocyclic rings, (for example mercapto triazoles), simple mercury salts, sulfonium mercury double salts and other mercury compounds. Azaindenes, preferably tetra or pentaazaindenes, particularly those which are substituted with hydroxyl or amino groups, are also suitable as stabilizers. Such compounds have been described in the article by Birr, Z.Wiss.Phot. 47, 2-58 (1952). Other suitable stabilizers are heterocyclic mercapto compounds, e.g., phenylmercaptotetrazole, quaternary benzothiazole derivatives, and benzotriazole.

The emulsions may be hardened in the usual manner, for example with formaldehyde or halogen substituted aldehydes which contain a carboxyl group, such as mucobromic acid, diketones, methanesulfonic acid esters, and dialdehydes.

The emulsions treated with the quaternary salts which contain a disulfide linkage, according to the invention may also contain color-forming couplers for the production of color photographic images.

The effect of the quaternary salts which contain a sulfide linkage, is usually not so marked in black-and-white and color developers. The reason for this is presumably that the salts decompose more rapidly, and in a different way, in the developer than they do in the emulsion.

EXAMPLE 1 Sample A: Comparison sample-without additive Sample B: 7 mg. of Compound 1V Sample C: 7 mg. of Compound 1X Sample D: 4 mg. of Compound X11 Sample E: 4 mg. of Compound XXII Sample F: 4 mg. of Compound 11 Sample G: 4 mg. of Compound XlV Sample 1-1: 4 mg. of Compound X1 Sample I: 4 mg. of Compound X111 Sample K: 4 mg. of Compound 111 Sample L: 4 mg. of Compound XV The afterripening is carried out to maximum sensitivity and the samples are made ready for casting by the addition of 600 mg. of saponin as wetting agent, 200 mg. of 4-hydroxy-6- methyl-1,3,3a,7-tetraazaindene as stabilizer and 10 ml. of a 10 percent aqueous formaldehyde solution as hardener, per liter of emulsion. The samples are then cast on cellulose acetate, exposed in a sensitometer behind a grey step wedge and developed at 20 C. in a developer of the following composition for 6 minutes:

Sodium sulfite sicc. 70.0 g. Na,B,O,-10H,O 7.0 g. hydroquinone 3.5 g p-monomethyl-aminophenol 3.5 g sodium citrate 7.0 g. potassium bromide 0.4 g

made up to 1 liter with water.

A difference of 3.0 represents a difference of one shutter stop.

EXAMPLE 2 An emulsion as described in Example 1 is divided into eight equal parts and the following compounds are added to the individual parts which are then ripened to maximum sensitivity: Sample A: Comparison samplewithout additive Sample B: 4 mg. of Compound 1 Sample C: 4 mg. of Compound V11 Sample D: 4 mg. of Compound X Sample E: 4 mg. of Compound X1 Sample F: 7 mg. of Compound XVI Sample G: 4mg. of Compound XlX Sample 1-1: 4 mg. of Compound XXI The samples are prepared for casting and developed as in Example 1.

TABLE 2 Sam p11: Senaitivity 'y-value fog fog (3 days 60 C.)

A Comparison 0,78 0,19 0,24

sample B +0,9 0.87 0,14 0.19 C +l,l 0,80 0,13 0.18 D +1.4" 0.87 0,16 0,19 E +l,8 0.86 0.16 0,17 F +l,2 0,84 0,14 0.15 G +l,7 0,88 0.13 0.18 H +03 0,86 0,15 0,16

A difference of 3.0 represents a difference of one shutter stop.

EXAMPLE 3 An emulsion as described in Example 1 is divided into 6 equal parts and the following compounds are added to the individual parts which are then ripened to maximum sensitivity. Sample A: Comparison samplewithut additive Sample B: 4 mg. of a compound of the formula CgH - ZHCI (according to US. Pat. No. 2,521,926) Sample C: 7 mg. of a compound of the formula Sample D: 4 mg. of Compound 1X Sample E: 4 mg. of a compound of the formula:

H5Cg Y 021111 Sample F: 7 mg. of Compound V.

The samples are prepared for casting and developing as in Example 1.

The behavior of the compounds as casting additives after completed ripening is described in this example. The following were added to a silver iodobromide gelatin emulsion which contained per kg. 60 g. of silver in the form of silver bromide with a silver iodide content of 6 mols percent:

600 mg. of saponin as wetting agent,

200 mg. of 4-hydroxy-6-methyl-1,3,3a,7tetraazaindene as stabilizer and 10 Sample F: 60 mg. of a compound of the formula 1 5 for comparison Sample G: 60 mg. of a compound of the formula H C\ 02115 N-CHzCH CH -S-S-CH;CHOH -N for comparison The casting solutions obtained were cast on a film support; they were exposed in a sensitometer behind a grey step wedge and developed for 6 minutes in a developer of the following composition:

Sodium sulfite sicc. 70 g.

Na,B,O,'l0l-1,0 7 g. hydroquinone 3.5 g. p-monomethylaminophenol 3.5 g. sodium citrate 7 g. potassium bromide 0.4 g. make up to 1 liter with water TABLE 4 40 Sample Sensitivity 7 fog A Comparison sample 0,96 0,10 13 +0.9 0,98 0.07 c +0.6 0,97 0.07 0 10 1.00 0,09 E +0,6 1,04 0.00

F 10 1,04 0.13 for G O,3 0,86 0,18 comparison A difference of 3.0 represents a difference of one shutter stop.

EXAMPLE 5 An emulsion as described in Example 4 was divided into four equal parts and the following compounds were added to the individual parts (base on 1 kg. of emulsion):

Sample A: Comparison samplewithout additive Sample B: 100 mg. of Compound V11 Sample C: 100 mg. of Compound IV Sample D: mg. ofCompound V The casting solutions obtained were cast and developed as in Example 4.

used as casting additive to the finished ripened emulsion do not cause any great increase in sensitivity, a marked reduction in fogging can be observed in this case, as it can be also when they are used as ripening agents (Examples 1-3 We claim:

1. A light-sensitive photographic material having at least one silver halide emulsion layer, characterized in that it contains a sensitizing amount of a compound of the following formula:

wherein R an alkyl radical having up to six carbon atoms; two R radicals attached to the same nitrogen atom may, with this nitrogen atom, form a 5-, 6- or 7-membered ring containing at least one hetero atom;

R an alkyl radical having up to six carbon atoms, or an aralkyl radical;

n an integer of from 1 to 6; an

X any anion;

X is absent when R contains a carboxylate group.

2. A light-sensitive photographic material according to claim I, wherein the silver halide emulsion layer in addition contains color couplers.

3. A light-sensitive photographic material according to claim 1, which contains a compound of the following formula:

4. A light-sensitive photographic material according to claim 1, which contains a compound of the following formula:

5. In the process for the production of photographic images in black-and-white or color by exposing a photographic material with at least one silver halide emulsion layer, developing in a black-and-white or color forming developer and fixing the improvement by which the development of the exposed photographic material takes place in the presence of a sensitizing amount of a compound of the following formula:

wherein R an alkyl radical having up to six carbon atoms; two R radicals attached to the same nitrogen atom may, with this nitrogen atom, form a 5-, 6- or 7-membered ring containing at 5 least one hetero atom;

' an alkyl radical having up to six carbon atoms, or an aralkyl radical;

n an integer of from i to 6;

X e any anion; X is absent when R contains a carboxylate group.

6. The process according to claim 5, wherein the development is carried out with a color forming developer in the presence of color couplers.

7. The process according to claim 5, wherein the development is carried out in the presence of a compound of the following formula:

8. The process according to claim 5, wherein the development is carried out in the presence of a compound of the following formula:

9. In the process for the production of photographic silver halide emulsions by precipitating the silver halide in the presence of a protective colloid, washing and chemical ripening, the improvement by which the chemical ripening is carried out in the presence of an effective amount of a compound of the following formula: 

2. A light-sensitive photographic material according to claim 1, wherein the silver halide emulsion layer in addition contains color couplers.
 3. A light-sensitive photographic material according to claim 1, which contains a compound of the following formula:
 4. A light-sensitive photographic material according to claim 1, which contains a compound of the following formula:
 5. In the process for the production of photographic images in black-and-white or color by exposing a photographic material with at least one silver halide emulsion layer, developing in a black-and-white or color forming developer and fixing the improvement by which the development of the exposed photographic material takes place in the presence of a sensitizing amount of a compound of the following formula: wherein R an alkyl radical having up to six carbon atoms; two R radicals attached to the same nitrogen atom may, with this nitrogen atom, form a 5-, 6- or 7-membered ring containing at least one hetero atom; R'' an alkyl radical having up to six carbon atoms, or an aralkyl radical; n an integer of from 1 to 6; X- any anion; X- is absent when R'' contains a carboxylate group.
 6. The process according to claim 5, wherein the development is carried out with a color forming developer in the presence of color couplers.
 7. The process according to claim 5, wherein the development is carried out in the presence of a compound of the following formula:
 8. The process according to claim 5, wherein the development is carried out in the presence of a compound of the following formula:
 9. In the process for the production of photographic silver halide emulsions by precipitating the silver halide in the presence of a protective colloid, washing and chemical ripening, the improvement by which the chemical ripening is carried out in the presence of an effective amount of a compound of the following formula: wherein R an alkyl radical having up to six carbon atoms; two R radicals attached to the same nitrogen atom may with this nitrogen atom form a 5-, 6- or 7-membered ring containing at least one hetero atom; R'' an alkyl radical having up to six carbon atoms or an aralkyl radical; n an integer from 1 to 6; X- any anion; X- is absent when R'' contains a carboxylate group. 